I will be your guide
by AlwaysNextToYou
Summary: "I know what you're going through isn't easy. But I swear we can help you. I will help you. Please, open this door. I promise everything's going to be alright." Sometimes we connect to someone when we least expect. (Will be a very long fic. Chapter 3 is up!)
1. Please

**Chapter 1 - "Please."**

"So what've we got?" Beckett and Castle were side by side, standing in front a dead body, Lanie was lowered next to it, her hands traveling through the blood and the bones, trying to figure out causes, but as soon as she heard Beckett's voice, she looked up to both of them.

"Claire Lott, 15 years old, time of death between 8 and 10pm." Lanie sighed slightly. "She was shot right in the heart, died immediately."

"She was… 15?" Castle opened his eyes a little, and then looked down to his feet, imagining that the girl could have been Alexis. This cases were always difficult to him.

"Yes, writer boy, you heard it well." Lanie frowned her eyebrow.

"Why would someone want to kill such a young girl?" he asked, looking at Lanie again, his eyes didn't need to travel much to get to her.

"That's what we need to find out." Beckett smiled lightly, knowing what was going on Castle's head. That was their thing - they always knew and understood each other. "Anyone heard the shot?"

"No. Someone saw it." Esposito walked behind them, and stood next to Beckett.

"What do you mean?" Beckett was quite surprised by that, since they weren't used to having witnesses. Not to that kind of murder.

"Mary Fillion. Also 15 years old. Apparently, the house is her aunt's. She lives here with her." he completed.

"Where is she right now?" Castle asked, interrupting Beckett, that was about to ask the same thing.

"She locked herself in her room. All we can hear are cries. She's scared. We've yelled, she doesn't open the door. We've called someone to open the door for us, someone that can get us a key. We don't want to scare her even more by kicking it."

"Well of course she's scared! She saw a friend die in her own house, for God's sake. I'll talk with her."

Beckett took a deep breath, and with Esposito's help, she got to the door, placing her ear next to it. It was normal for a 15 year old to be shocked with such thing. She knew what she was going through wasn't easy. A sigh escaped from her lips before she started talking.

"Mary?" she started, yelling. "Detective Kate Beckett here," she added, shouting a look at Esposito as she heard the girl cry. "I need you to open this door for me, okay? I know you're scared, but we can help you."

"Come on', just open the door." Esposito tried to complete her. No, that was Castle's thing. It wouldn't work with him.

"Mary, listen to me. I know what you're going through isn't easy. But I swear we can help you. I will help you. Please, open this door. I promise everything's going to be alright."

She completed her speech, now she hoped the young girl would open the door. That was all she could do. She really wanted to help this girl. She knew the pain.

Suddenly she saw the young girl opening the door; a small smile appeared on Beckett's lips, realizing she had convinced her. Esposito approached the young girl, grabbing her arm, not with too much strength so he wouldn't hurt her. He slowly walked her out of the house and leaded her into the police car, trying to be careful with her, treat her well, as Beckett walked towards Castle again, without looking back. She was deeply worried about this girl for some reason. Castle was trying to help Lanie but all he could do was staring like a madman and shout his crazy theories, something that Lanie didn't appreciate that much.

"Oh thank God," Lanie got up as she saw Beckett approaching. "Take this man out of here, please." she pushed Castle towards the brunette.

"I will miss you too." he shouted as him and his partner walked out of the house and headed to the precinct.

* * *

"Let's go, Castle." she shouted a smile, and then he opened the interrogation room's door for her, as she thanked him, almost whispering. They walked towards the table, Mary sitting on a chair next to it, tears rolling down her face, lots of them coming quickly without warnings. They both sat on chairs, right in front of the 15 year old girl. It was time for some questions, even though they knew it wasn't going to be easy.

"I'm sorry you're in here," Castle smiled lightly. "But it's for security. You're not a suspect or anything like that." he said, making sure she knew she wasn't. He wanted to keep her calm, but her heart started beating faster, tears coming down stronger. It was a reminder her friend was dead.

"We're here to help you, Mary. I promise we'll do our best to catch the guy. But we also need your help, okay?" Beckett looked into the girl's eyes as she looked up.

"Okay." Finally someone was able to make the girl talk. First time they had actually heard her voice. She hadn't talked since she was out of the room.

"I'm going to ask you a few questions, is that alright?"

"Yes." she mumbled as she tried to wipe her tears away.

"You live with your aunt. Why?" Beckett asked as she interlaced her fingers, placing her hands on the table.

"My parents died exactly one year ago. It was a robbery gone wrong. At least that's what they said. I don't believe it much." she looked down, tears streaming down her face again, but she tried to keep them to herself, so she wouldn't look like a complete mess in front of her... well, idol. This young girl had a passion for Rick Castle - not only he was her favorite writer, he was also very charming and some kind of writer role model for her.

"I'm really sorry about that," Beckett said, her hand travelling through the table, letting it open right next to hers, so she'd hold it. A light smile appeared on Mary's lips and she took Beckett's hand, thankful for her action. "What did you see?" she asked, holding her hand with all her strength, now going deeper.

"She said she needed to go to the bathroom. I turned on the radio and sat on the sofa as I read… uh... Naked Heat." she shouted a look to Castle and smiled shyly, then continued. "I heard her scream and then I ran towards the bathroom. In a few moments I had a gun pointed at my head and he started stepping back. He jumped out of the window, and when I looked at her… she was dead." she let Beckett's hand go, and placed both of her hands in her head. "I could have stopped him from running away."

"You had a gun pointed at your head," she pointed out.

"You did what everyone would do. You can't blame yourself." Castle said, looking at Beckett.

"I think we have enough for now." Beckett smiled. "Detectives Ryan and Esposito will lead you to another room where you'll stay until we catch the guy."

"I'm scared." she admitted as she grabbed Beckett's hand again when she was about to get up, a tear falling right on it.

"I promise you'll be safe." she rubbed Mary's hand as she looked at Castle and nodded, then let it go and got up, walking out of the interrogation room, Castle once again, opening the door for her, like the gentleman he was.

* * *

_Notes: I know it's not a big thing, but I wanted to keep Chapter One quite short so people would understand what happened here. I will post the next chapter (which will have Caskett cute moments) as soon as I get enough reviews to improve my writing and keep my imagination going. I have lots of sweet moments coming up, and just so you know, Mary will be part of a couple of them. Review please! :)_


	2. What if

**Chapter 2 - "What if"**

"I can't leave her here, Castle." Kate sat next to her desk as she ran her fingers by her hair. She had no idea how to help this girl, but she wanted to. She needed to.

"You've already done the best you could." he pointed out, sitting next to her, a smile appearing on his face as his eyes quickly traveled through her whole body. She was definitely hot when she was worried.

"She'll be alone in that room... and she'll cry." the brunette picked up a pen and started drawing non-sense lines as she thought. Millions of thoughts were travelling through her head, but nothing seemed to be enough. Nothing seemed to be right. "I need to help her."

"Yeah, maybe." Castle was staring at her body, his eyes going from her head to her feet, a smile playing across his lips, sometimes even biting the lower one, enjoying his view. If they weren't in the precinct, God knows what he'd do to her.

"Any ideas, Castle?" she asked, turning her head towards her partner as she let the pen go and it rolled across the table.

"A couple." he licked his bottom lip, lost in his imagination.

"Castle!" Beckett shouted his name loud and clear, making him gasp and look into her eyes. She then rolled hers, slightly furious but in need to laugh at the way he was looking at her. She knew he was fancying about her. "I meant about the girl."

"Oh, uh... Leave her here. She'll be safe, I'm sure." he wasn't really thinking about the case. Nope, not at all.

"I can't." she insisted. "I think I'm taking her home with me."

"What?" those words definitely got his attention Taking the girl home with her? That would mean no fun. His plans were most times ruined during the week thanks to his mother and his daughter, and now her house was going to have someone in it too? He couldn't let that happen.

"Yes, Castle. I mean, the killer won't obviously search for her in my house." Castle's plans were definitely ruined. Beckett believed this was the best decision, and it would, probably work. "I just need to be discrete when I take her there. She'll be safe and have company. I mean, the poor girl will probably go to an orphanage after this."

"Kate, no." he grabbed her by the arm, making her chair roll in his direction, and their faces were pretty close now. "She'll be safe here, it's the best for her. All you have to do is find who the killer is, not taking care of her."

"Alexis."

"Where?" he turned around, his eyes traveled through the whole room, but no sign of her. He looked back at Kate, shouting a confused look.

"No, I mean... what if it was Alexis? What if she lost you? Would you like her to be alone in a room, crying?" Beckett had a point. She needed to help this girl, and mostly, because she was connected with her in some way that she couldn't explain.

" I wouldn't like that, no. But I'd be dead so I wouldn't like or dislike anything." that made Kate giggle. But her wide smile slowly turned into a light one, a very tender one. He was the only person able to do that to her, in the middle of a serious conversation.

"I know what you were thinking," she whispered, then smiled a little more and continued. "But I think it can wait for tomorrow." one of her hands slid to his shirt, and played with the buttons of it. "And I promise I'll reward you..."

"Uh- good." he mumbled, watching her moves closely and at the same time, enjoying the tender smile on her face turning into a provocative one. In a few moments, he felt her pulling away and getting up.

"I'm going to talk with Gates now, see if she allows me to take her with me." the brunette detective turned around after picking up her jacket, a smile still playing across her lips. She enjoyed teasing him.

"Alright." his eyes slid from her hair, as she turned around, to her butt, staring at it as she walked. One night. He only needed to wait one night to own her body again.

Beckett knew what he was looking at. He always did, and not in a discrete way. "And... Castle?" she slowly turned around and smiled. "Thanks for supporting me."

"Always."

* * *

_Note: Hope you enjoyed this little chapter. I'll post the next one today, if not, tomorrow morning. I'm very happy with how this is turning out, and I feel quite excited to keep writing and developing Mary as a character and Caskett as a __couple. So, more cute moments between them will happen, and this was just something to help with the case, also with the fact that I want Mary to be more in the story, to mark her point. Reviews would be nice, but if you don't want to, it's fine, just keep following the story if you like it! :)_


	3. Protected

**Chapter 3 - "Protected"**

Kate walked in a large room, white walls and floor, a bed next to one of the walls, as well as a table and a chair. It was a very simple room, but there was something somehow angelical about it. Not that people were used to be in it for the right causes: most of the people, if not all, had been in this room because they had no where else to go while they were being investigated. Mostly witnesses, of course.

"Mary?" the brunette stopped walking, and looked at the young blonde girl sitting in the bed, looking down to her bare feet as they touched the floor.

She looked up. Her blue eyes were somehow begging for help, and Beckett could see she was scared. This girl knew that the killer was probably after her. She was smart, even though she was still young. Too young to deal with murders.

"I'm going to take you with me." she started, giving a few steps towards her, so they wouldn't be that distant. Her hair was falling perfectly on her shoulders, and her clothes fit her like a glove.

"Where?" the blonde girl stood on her feet, her dress falling to her knees as she took her hair from her face, using her hand softly.

"You're coming to my house," Beckett didn't need to think much about the response she was going to give her. "I know it's odd, but I believe it's the best for you. I _promise _you'll be safe there."

"He's after me, isn't he?" she finally asked, words coming from her mouth like bombs, ready to explode. Her eyes were now full of tears, that she was trying to hold back.

"We don't know for sure. But I guarantee you... we'll catch the guy."

"Alright." a little smile appeared on the blonde's lips for a second, then quickly disappeared as Beckett turned around, not sure of what to do or how to act.

"Come on." she nodded her head as she looked to a cop standing by the door, and he let both of them leave the room, Beckett always leading the way.

* * *

"You're calling Rick Castle," he rolled his chair towards his table as he picked up the phone, a smile playing across his lips, knowing it was probably Kate, but not sure, since he didn't even take a look at the screen.

"Yeah, I was pretty sure I was calling you, writer boy." he immidientely recognized this voice, and a small laugh escaped from his lips.

"Ooh, Lanie. Is your house burning? Because you're calling _me._" Surprised? Very. He wasn't definitely used to getting calls from Lanie.

"Grow up." she said without thinking much, he knew that she was probably rolling her eyes as she always did.

"So, what did I do to deserve this call?" he asked, running his fingers through his hair once.

"Are you with Beckett?" she seemed to be somehow worried.

"No, she's at home." he quickly replied.

"What? Shouldn't she be working?" her voice was a little high pitched, shouting in confusion and surprise.

"She's working... at home. Beckett took our witness with her. The girl was scared and she thought it'd be good for her to have some company and you know, she'd feel safe." Castle didn't seem to be excited about it. He rested his hand on the table and sighed slightly.

"Oh. Alright. Call me when she goes to the precinct."

"Yeah, yeah. I will." the famous novelist ran his fingers through his hair, pushing it back, giving a quick reminder to himself that he needed a hair cut. "Thanks for calling."

In a couple of seconds, the call was over, and Rick Castle was now wondering what was happening in Beckett's house.

* * *

"Here we are," Beckett opened the door for Mary, revealing her house, a smile playing across her lips, somehow wondering what was going on in the girls' mind. She was young, broken, fragile, scared. Everytime she looked at her, she somehow saw herself when she lost her mother.

"This is beautiful." she said weakly, a smile trying to form in her lips as she turned around to look at Beckett, that was closing the door behind them. "Thank you, detective Beckett."

"I'm just doing my job." she responded, now facing the girl.

"No, you're not." a smile was finally able to form in her lips as she looked down to her feet shyly. "Your job is to find out who the killer is, not taking care of me." she looked up to Beckett again, her eyes meeting hers, trying to thank her deeply with one look.

"It's the least I can do." she assured the young girl, then took a step. "Make yourself home."

"Thanks, detective." she turned around, now her backs were facing the brunette detective, as her eyes traveled through the room, trying to notice every detail. Mary liked how the house was decorated. It was so... _her._

"You know, you can call me Kate. Or Beckett." a small laugh escaped from Beckett's lips, noticing how the young girl was looking at the house, but staying still, not moving a single muscle of her body. "You must be hungry. What do you want to eat?" she asked, walking towards the fridge.

"Oh, uh... whatever you have." the fifteen year old walked towards the table standing near the wall, then sat on one of the chairs as she rested her hands on her lap. "I'm not that hungry." her voice was low, because she couldn't help but to feel shy around Beckett.

Mary was one of Castle's biggest fans, and she obviously knew that Nikki Heat was based on Beckett. And even though she wasn't in her house because of the best reasons, it was almost like she was feeling blessed and thankful that this one detective got the case on her hands. Not only because she was Nikki Heat, but because she felt secure, almost like nothing would get to her if she was near her. And that was a good feeling. Something she didn't feel for a while. Because she used to feel like that when she was with her mother.

She took her hands from her lap and placed them on the table, Beckett walking towards her with two bowls on her hands, a smile playing across her lips, her hair jumping a bit sometimes then falling on her shoulders perfectly as she walked.

"Ice cream always makes me feel better." the brunette sat next to Mary and handed her one of the bowls.

"It's my favorite," she admitted, looking down to her own legs shyly after grabbing the bowl. "Thank you."

"I think you've thanked me about one hundred times today." Beckett laughed once.

Silence took over the room, and the next 15 minutes were spent like that: simply eating ice cream as they tried to understand what was going on in each other's minds. Mary was thankful, and she didn't think much about the reason she was there. No more crying for a while. Because she was truly feeling _protected._

* * *

_Note: Whoop, I'm quite happy about the follows this story has been getting, and thankful. I had the idea for this story even before season 4 premiered, so yeah, I'm finally writing it! Next chapter soon. More Caskett moments will come, I promise. Also Beckett/Mary relationship will slowly grow, and I have a few surprises coming... Stay tuned! Reviews will be nice._


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